L2TP VPN client via NetworkManager can't hold connection.

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starcat
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Joined: Wed Jul 03, 2019 4:49 am

L2TP VPN client via NetworkManager can't hold connection.

Post by starcat » Wed Jul 03, 2019 7:21 am

Hello!
I have tried to find an answer by this forum or others but without result. Sorry if it duplicate something somewhere here and for my low English.

I have create the connection to my l2tp server 195.1XX.XX.XXX. Connection getting up successfully. But it going down in few seconds. Connection terminated by server for no lcp-relpy from my "client". As I can see in dump replies are going out. But they go to ppp interface of tunnel instead of eth\wlan\ppp interace via which the connection established.

This happens on

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DISTRIB_ID=LinuxMint
DISTRIB_RELEASE=19
DISTRIB_CODENAME=tara
DISTRIB_DESCRIPTION="Linux Mint 19 Tara"
And on my laptop with 19.1.


Before connection I have (for example) such routing table

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default via 192.168.75.1 dev enp4s0 proto static metric 100 
169.254.0.0/16 dev enp4s0 scope link metric 1000 
192.168.75.0/24 dev enp4s0 proto kernel scope link src 192.168.75.2 metric 100 
After connection established

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default via 192.168.75.1 dev enp4s0 proto static metric 100 
169.254.0.0/16 dev enp4s0 scope link metric 1000 
192.168.75.0/24 dev enp4s0 proto kernel scope link src 192.168.75.2 metric 100 
192.168.75.1 dev enp4s0 proto static scope link metric 100 
192.168.80.0/24 dev ppp0 proto static scope link metric 50 
195.1XX.XX.XXX dev ppp0 proto kernel scope link src 192.168.80.104 metric 50 
195.1XX.XX.XXX via 192.168.75.1 dev enp4s0 proto static metric 100 

Route

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192.168.80.0/24 dev ppp0 proto static scope link metric 50 
added manually via NM configuration for this l2tp connection. Same for pptp.
I don't use tunnel as default gateway.

The priority route to vpn server going to ppp0 of tunnel and not to enp4s0.

With pptp client to the same server it hold good. But routing table have one more additional route. I have marked it with "<---"

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default via 192.168.75.1 dev enp4s0 proto static metric 100 
169.254.0.0/16 dev enp4s0 scope link metric 1000 
192.168.75.0/24 dev enp4s0 proto kernel scope link src 192.168.75.2 metric 100 
192.168.75.1 dev enp4s0 proto static scope link metric 100 
192.168.80.0/24 dev ppp0 proto static scope link metric 50 
195.1XX.XX.XXX via 192.168.75.1 dev enp4s0 src 192.168.75.2      <---
195.1XX.XX.XXX dev ppp0 proto kernel scope link src 192.168.80.104 metric 50 
195.1XX.XX.XXX via 192.168.75.1 dev enp4s0 proto static metric 100 
After pptp disconnected this route stays in system

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default via 192.168.75.1 dev enp4s0 proto static metric 100 
169.254.0.0/16 dev enp4s0 scope link metric 1000 
192.168.75.0/24 dev enp4s0 proto kernel scope link src 192.168.75.2 metric 100 
195.1XX.XX.XXX via 192.168.75.1 dev enp4s0 src 192.168.75.2 
And if I launch l2tp (after pptp con\disc) lcp does successfully with this route.

Windows\Mac0S clients have no any issues with this server.

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